Alternating AVE segments with segments of conventional track or of lower specifications occurs at other points of the line. The Alvia train between Madrid and Ferrol, the fastest going through Santigo, travels on different tracks. Between Madrid and Olmedo (Valladolid) it takes advantage of the AVE track. Then, between Olmedo and Ourense it returns to a conventional track, waiting for the completion of the AVE works already underway. Finally, between Ourense and Ferrol it again joins the AVE line, which at the entrance to Santiago goes alongside the old track.

At that moment, the train must brake and when it reaches the tight bend where the accident took place it must leave it speed at barely 80km/h. The velocity drop at that point is very steep: form 200 km/h to 80 in a short time span.

The causes of the excessive speed are still not known. The line where the accident occurred is still not within the ERTMS (European Rail Traffic Management System), a rail traffic mnagement system preventing a train from exceeding the established speed limit or disobey stop signals, very similar to the automatic alert systems already installed in many European countries. This system is the one deployed, for instance, on the Madrid-Barcelona AVE line in october 2011. (translation by Migeru at the European Tribune)

The statement "the cause of the excessive speed are still not know" is referring to the proximate cause, since the ultimate cause is stated directly after: the line is not within the version of Positive Train Control signal system used in Europe, the ERTMS.